diff --git a/lib/isc/include/isc/lex.h b/lib/isc/include/isc/lex.h
index b4199a3236..4070b0385d 100644
--- a/lib/isc/include/isc/lex.h
+++ b/lib/isc/include/isc/lex.h
@@ -15,7 +15,7 @@
  * SOFTWARE.
  */
 
-/* $Id: lex.h,v 1.19 2000/06/22 21:57:39 tale Exp $ */
+/* $Id: lex.h,v 1.20 2000/07/10 05:11:18 marka Exp $ */
 
 #ifndef ISC_LEX_H
 #define ISC_LEX_H 1
@@ -342,6 +342,20 @@ isc_lex_getsourceline(isc_lex_t *lex);
  * 	Current line number or 0 if no current source.
  */
 
+isc_boolean_t
+isc_lex_isfile(isc_lex_t *lex);
+/*
+ * Return whether the current input source is a file.
+ *
+ * Requires:
+ *	'lex' is a valid lexer.
+ *
+ * Returns:
+ * 	ISC_TRUE if the current input is a file,
+ *	ISC_FALSE otherwise.
+ */
+
+
 ISC_LANG_ENDDECLS
 
 #endif /* ISC_LEX_H */
diff --git a/lib/isc/lex.c b/lib/isc/lex.c
index 80395fa56f..5a838a9a77 100644
--- a/lib/isc/lex.c
+++ b/lib/isc/lex.c
@@ -15,7 +15,7 @@
  * SOFTWARE.
  */
 
-/* $Id: lex.c,v 1.31 2000/06/23 22:32:10 brister Exp $ */
+/* $Id: lex.c,v 1.32 2000/07/10 05:11:17 marka Exp $ */
 
 #include <config.h>
 
@@ -718,3 +718,17 @@ isc_lex_getsourceline(isc_lex_t *lex) {
 
 	return (source->line);
 }
+
+isc_boolean_t
+isc_lex_isfile(isc_lex_t *lex) {
+	inputsource *source;
+
+	REQUIRE(VALID_LEX(lex));
+
+	source = HEAD(lex->sources);
+
+	if (source == NULL)
+		return (ISC_FALSE);
+
+	return (source->is_file);
+}